The present invention relates to a burner for pulverized coal and more particularly to a stationary coal nozzle for a burner on a pulverized coal fired furnace.
A wide variety of burner designs have been developed over the years for burners used in furnaces, boilers and the like for burning pulverized coal. Problems incurred in burning pulverized coal often can be associated with coal roping in the fuel delivery system. Fuel roping is believed to be caused by centrifugal flow patterns established by elbows and pipe bends.
Coal roping causes poor fuel distribution exiting the nozzle tip or outlet which results in flame variations. These flame variations range from substoichiometric fuel rich zones, where the reducing atmosphere contributes to slagging and water wall erosion, to high oxygen zones, which potentially create high thermal generation oxides of nitrogen. With these wide variations at each burner of a multiple burner unit, unit control is difficult.
In an attempt to reduce nitrogen oxide levels and to reduce fuel roping, many stationary coal nozzles and nozzle tips have been developed over the years. For example, see U.S. Pat. Nos. 4,348,170; 4,380,202; 4,479,442 and 4,634,054. All of these references have attempted to disrupt the coal roping flow into and out of the stationary coal nozzles with limited success.
In an attempt to provide better fuel distribution, other manufacturers have provided an elongated longitudinal rib down the bottom center of the nozzle. However, this configuration also has failed to provide the desired reduction in fuel roping.
It is accordingly a major object of the present invention to provide a stationary coal nozzle designed which provides more uniform fuel distribution exiting the nozzle tip into the furnace combustion zone.